package com.study.suanfa;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Set;

/**
 * @description: HashMapAndTreeMapTetst
 * @date: 2020/11/11 19:46
 * @author: hcm
 * @version: 1.0
 */
public class HashMapAndTreeMapTetst {

    public static void main(String[] args) {
        HashMap map = new HashMap();
        map.put(null,null);

        Hashtable hashtable = new Hashtable();
        hashtable.put(null,"");
        Set set = new HashSet();
        set.add(null);
    }
}
